Generally, rubber compositions used in manufacture of rubber articles such as tires, conveyor belts, anti-vibration rubbers and seismic isolation rubbers are required to have high elastic modulus, from the viewpoint of improving the stability during usage or operation of the rubber article. In order to satisfy such requirement, various rubber compositions have been developed.
For example, PTL1 (JP2006-117927A) discloses compounding 30 to 100 parts by mass of a carbon black per 100 parts by mass of a rubber component in which a diene based rubber is a main component, a Novolak type phenol based resin, and a curing agent for resin as a methylene provider, to thereby obtain a rubber composition having a high elastic modulus.
Moreover, PTL2 (JP2008-024952A) discloses compounding at a specific a reinforcing agent, and a rubber component consisting of a short fiber like 1,2-polybutadiene having a melting point of 170° C. or higher, a polymer having a melting point of 150° C. or lower, and a diene based rubber, to thereby obtain a rubber composition having a high elastic modulus.
Further, PTL3 (JPH7-133376A) discloses compounding a rubber containing a diene based monomer with an alloyed polyethylene having an ultrahigh molecular weight, to thereby obtain a rubber composition having a high dynamic elastic modulus and a low heat build-up.